Merck Refiling Gedapixant NDA Next Year

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Merck says it will file a response in the first half of 2023 to an FDA complete response letter it received in January on an NDA for gefapixant, an orally administered selective P2X3 receptor antagonist for treating refractory chronic cough or unexplained chronic cough in adults. The company says it is performing additional analyses, which will be submitted in its response. The letter reportedly requested additional information related to the cough counting system that was used to assess efficacy, and it did not cite any issues related to gefapixant’s safety.

Merck says that a refractory chronic cough is one that persists despite appropriate treatment of underlying conditions and an unexplained chronic cough is one where the underlying cause cannot be identified despite a thorough evaluation.

P2X3 receptors are one of the receptor types found on sensory nerve fibers, predominantly C fibers, in the airway lining, according to the company. “Chemical stimuli, including adenosine triphosphate (ATP), can be released from airway lining cells due to airway inflammation, irritation and mechanical stress/injury,” it says. “The inhibition of binding of extracellular ATP to P2X3 receptors is thought to reduce sensory nerve activation and, subsequently, cough.”

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